There has been an increasing amount of research into the use of organic materials in electronic and optoelectronic devices, examples of such devices include organic electroluminescent devices, as disclosed in WO90/13148 and U.S. Pat. No. 4,539,507, organic photovoltaic devices, as disclosed in U.S. Pat. No. 5,670,791 and organic transistors as disclosed in WO01/47043. Organic semiconductive and conductive polymers have proven to be of particular use in organic electronic and optoelectronic devices due in large part to their processability and in particular their solution processability which enable them to be formed into devices using a range of coating and printing techniques. The use of such techniques gives rise to the potential for low cost, easily manufacturable polymeric organic electronic and optoelectronic devices, such as displays and plastic microchips. Ink-jet printing has recently emerged as an important method in the preparation of organic electronic and optoelectronic devices, ink-jet printed organic electroluminescent devices are disclosed in EP0880303 and ink-jet printed transistors in the aforementioned WO01/47043.
The preparation of organic electronic and optoelectronic devices by solution processing requires a high degree, of pattern resolution, of the order of 10 microns. To achieve such high levels of resolution using solution processing techniques it has been found necessary to provide relief patterns on the substrates onto which the organic material is to be coated or printed, these relief pattern prevent the organic material spreading into unwanted areas. EP0980778 discloses relief patterns in the form of banks of photoresist which allow semiconductive polymers to be deposited in series of parallel lines, it has been found that the surface properties of the substrate and the material of the relief pattern have a great influence on the behaviour of the deposited organic material. It is desirable that the material of the substrate has a wetting surface and so becomes coated with the deposited solution of organic material,the solution of organic material then has a low contact angle on the surface of the material of the substrate, and it is desireable that the material of the relief pattern has a non-wetting surface and so does not become coated with the deposited solution of organic material, the solution of organic material then has a high contact angle on the surface of the substrate. In particular for depositing organic materials on selected areas of a substrate the difference in contact angles between regions where it is desired to deposit the organic material and regions where it is not desired to deposit the organic material should be a large as possible. In the aforementioned EP0989778 a relief pattern of a polyimide photoresist in the form of banks is formed on a glass substrate coated with a layer of indium-tin oxide (ITO) this patterned substrate is exposed to a O2/CF4 plasma treatment which increases the contact angle of the solution of organic material at the polyimide and decreases the contact angle of the solution of organic material at the ITO, allowing aqueous solutions of semiconductive or conductive polymers to be deposited into the channels formed by the banks without overflowing into neighbouring channels or into unwanted areas.
Although the above mentioned O2/CF4 plasma treatment of substrates having polyimide relief patterns has become established as the method of choice in preparing substrates for organic electronic and optoelectronic devices the process has a number of disadvantages in that it requires relatively complex processing equipment, such as vacuum and plasma systems, and use of environmentally harmful gases. Further although it is thought that the treatment results in a partial fluorination of the surface of the polyimide material, as discussed in U.S. Pat. No. 5,904,154, this fluorination is only temporary and the surface properties of the polyimide change over time. Additionally the O2/CF4 plasma treatment must be carried out over a period of time of the order of tens of minutes, such long processing times are thought to have a deleterious effect on the lifetime of the organic electronic or optoelectronic devices. Another disadvantage of the prior art O2/CF4 plasma process is that it must be carried out as a batch process in a vacuum chamber whereas it is generally preferred to use continuous processes which may be readily integrated into production lines. This disclosure provides a method for the preparation of substrates for organic electronic and optoelectronic devices which provides permanently fluorinated relief features, does not require prior conditioning of the surface relief features, nor does it require complex equipment or environmentally harmful gases, it allows shorter processing times and may be operated as a continuous process.